Checking an exhaust gas flap

1. A method for checking a valve of an exhaust gas turbocharger of an internal combustion engine, wherein an exhaust gas flow exits the internal combustion engine, and wherein a first portion of said flow flows through a turbine of the exhaust gas turbocharger into an exhaust gas system and a second portion flows through the valve into the exhaust gas system, said method comprising:

varying a fuel-to-air ratio in a fresh gas supplied to the internal combustion engine;

determining a residual oxygen content in the exhaust gas system;

determining a variation of the residual oxygen content; and

determining that the valve is faulty in response to determining that the variation of the residual oxygen content does not follow the variation of the fuel-to-air ratio in the fresh gas in a predetermined manner.

2. The method of claim 1 , wherein the fuel-to-air ratio is varied during an operating state of the internal combustion engine in which the valve is activated to be partially open.

3. The method of claim 1 , the fuel-to-air ratio is varied according to a predetermined periodic pattern.

4. The method of claim 1 , wherein the predetermined manner is stored in a memory and wherein the variation of the residual oxygen content is compared with the stored predetermined manner.

5. The method of claim 4 , comprising determining the predetermined manner based on a preceding measurement of the residual oxygen content in the exhaust gas system of a corresponding internal combustion engine during a corresponding variation of the fuel-to-air ratio when the valve is functional.

6. The method of claim 1 , comprising determining the predetermined manner based on a detected duration for exhaust gas to flow through the turbine and through the valve.

7. The method of claim 1 , further comprising:

determining a desired position of the valve;

detecting a boost pressure of the exhaust gas turbocharger; and

determining that the boost pressure does not correspond to the desired pressure.

8. A device for checking a valve of an exhaust as turbocharger of an internal combustion engine, wherein an exhaust gas flow exits the internal combustion engine, and wherein a first portion of said flow flows through a turbine of the exhaust gas turbocharger into an exhaust gas system and a second portion flows through the valve into the exhaust gas system, said device comprising:

a control device configured to vary a fuel-to-air ratio in a fresh gas supplied to the internal combustion engine;

a sampling device configured to determine a residual oxygen content in the exhaust gas system; and

a processing device configured to:

determine a variation of the residual oxygen content; and

determine that the value is faulty in response to determining that the variation of the residual oxygen content does not follow the variation of the fuel-to-air ratio in the fresh gas in a predetermined manner.

9. The device of claim 8 , wherein the device is configured to control an operating state of the internal combustion engine.

10. The device of claim 8 , wherein the control device is configured to vary the fuel-to-air ratio during an operating state of the internal combustion engine in which the valve is activated to be partially open.

11. The device of claim 8 , wherein the control device is configured to vary the fuel-to-air ratio according to a predetermined periodic pattern.

12. The device of claim 8 , comprising a memory storing the predetermined manner, wherein the processing device is configured to compare the variation of the residual oxygen content with the stored predetermined manner.

13. The device of claim 12 , wherein the processing device is configured to determine the predetermined manner based on a preceding measurement of the residual oxygen content in the exhaust gas system of a corresponding internal combustion engine during a corresponding variation of the fuel-to-air ratio when the valve is functional.

14. The device of claim 8 , wherein the processing device is configured to determine the predetermined manner based on a detected duration for exhaust gas to flow through the turbine and through the valve.

15. The device of claim 8 , wherein the processing device is configured to:

determining a desired position of the valve;

detecting a boost pressure of the exhaust gas turbocharger; and

determining that the boost pressure does not correspond to the desired pressure.

16. A computer program product for checking a valve of an exhaust gas turbocharger of an internal combustion engine, wherein an exhaust gas flow exits the internal combustion engine, and wherein a first portion of said flow flows through a turbine of the exhaust gas turbocharger into an exhaust gas system and a second portion flows through the valve into the exhaust gas system, the computer program product comprising computer instructions stored in non-transitory computer-readable media and executable by a processor to:

vary a fuel-to-air ratio in a fresh gas supplied to the internal combustion engine;

determine a residual oxygen content in the exhaust gas system;

determine a variation of the residual oxygen content; and

determine that the valve is faulty in response to determining that the variation of the residual oxygen content does not follow the variation of the fuel-to-air ratio in the fresh gas in a predetermined manner.